CVE-2017-5521 in R8500
Summary
by MITRE
An issue was discovered on NETGEAR R8500, R8300, R7000, R6400, R7300, R7100LG, R6300v2, WNDR3400v3, WNR3500Lv2, R6250, R6700, R6900, and R8000 devices. They are prone to password disclosure via simple crafted requests to the web management server. The bug is exploitable remotely if the remote management option is set, and can also be exploited given access to the router over LAN or WLAN. When trying to access the web panel, a user is asked to authenticate; if the authentication is canceled and password recovery is not enabled, the user is redirected to a page that exposes a password recovery token. If a user supplies the correct token to the page /passwordrecovered.cgi?id=TOKEN (and password recovery is not enabled), they will receive the admin password for the router. If password recovery is set the exploit will fail, as it will ask the user for the recovery questions that were previously set when enabling that feature. This is persistent (even after disabling the recovery option, the exploit will fail) because the router will ask for the security questions.
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Analysis
by VulDB Data Team • 02/04/2025
The vulnerability identified as CVE-2017-5521 represents a critical authentication bypass flaw affecting multiple NETGEAR router models including R8500, R8300, R7000, and numerous others. This issue stems from improper handling of password recovery mechanisms within the web management interface, creating a persistent security weakness that can be exploited remotely or locally. The vulnerability manifests when users attempt to access the router's web panel and cancel authentication, triggering a redirect to a password recovery page that inadvertently exposes administrative credentials.
The technical implementation of this flaw involves the router's web server failing to properly validate authentication states before presenting password recovery tokens. When authentication is canceled, the system generates and displays a recovery token that can be used to retrieve administrative passwords through the /passwordrecovered.cgi endpoint. This design flaw violates fundamental security principles by exposing sensitive authentication data without proper authorization verification. The vulnerability operates at the application layer and specifically targets the web interface authentication flow, making it particularly dangerous as it bypasses normal user authentication mechanisms entirely.
The operational impact of this vulnerability extends beyond simple credential exposure, as it enables unauthorized remote access to network infrastructure. Attackers can exploit this weakness without requiring physical access or prior knowledge of administrative credentials, making it particularly concerning for enterprise and residential network environments. The vulnerability's persistence is notable since even after disabling password recovery features, the system continues to require security questions that were established during the initial configuration, indicating a deeper architectural flaw in how the router handles authentication state management. This characteristic makes the vulnerability resistant to simple configuration changes and requires complete firmware reinstallation to fully remediate.
From a cybersecurity perspective, this vulnerability aligns with CWE-287 (Improper Authentication) and represents a classic case of insecure direct object reference where the system fails to properly validate user authorization before granting access to sensitive functions. The attack pattern corresponds to techniques described in the MITRE ATT&CK framework under credential access and privilege escalation domains, specifically targeting the exploitation of weak authentication mechanisms. Organizations should implement immediate mitigations including disabling remote management features, changing default credentials, and applying vendor-provided firmware updates. Network segmentation and monitoring for unauthorized access attempts can help detect exploitation attempts, while regular firmware updates remain the most effective long-term solution to address this persistent authentication bypass vulnerability affecting multiple NETGEAR router models across different generations.